1. Field of the Invention
The present invention relates to, for example, a semiconductor, a transistor, and a semiconductor device. Alternatively, the present invention relates to, for example, methods for manufacturing a semiconductor, a transistor, and a semiconductor device. Further alternatively, the present invention relates to, for example, a semiconductor, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, a processor, and an electronic device. Still further alternatively, the present invention relates to methods for manufacturing a semiconductor, a display device, a liquid crystal display device, a light-emitting device, a memory device, and an electronic device. Yet still further alternatively, the present invention relates to driving methods of a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a memory device, and an electronic device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A display device, a light-emitting device, a lighting device, an electro-optical device, a semiconductor circuit, and an electronic device include a semiconductor device in some cases.
2. Description of the Related Art
A technique for forming a transistor with the use of a semiconductor over a substrate having an insulating surface has attracted attention. The transistor is applied to a wide range of semiconductor devices such as an integrated circuit and a display device. Silicon is known as a semiconductor applicable to a transistor.
As silicon which is used as a semiconductor of a transistor, either amorphous silicon or polycrystalline silicon is used depending on the purpose. For example, in the case of a transistor included in a large display device, it is preferable to use amorphous silicon, which can be used to form a film on a large substrate with the established technique. In the case of a transistor included in a high-performance display device in which a driver circuit and a pixel circuit are formed over the same substrate, it is preferable to use polycrystalline silicon, which can be used to form a transistor having a high field-effect mobility. It is known that polycrystalline silicon can be formed as a result of heat treatment at high temperatures or laser light treatment on amorphous silicon.
In recent years, transistors including oxide semiconductors (typified by an In—Ga—Zn oxide) have been actively developed.
Oxide semiconductors have a long history, and in 1985, synthesis of an In—Ga—Zn oxide crystal was reported (see Non-Patent Document 1). In 1988, it was disclosed to use an In—Ga—Zn oxide crystal for a semiconductor element (see Patent Document 1). It was reported in 1995 that an In—Ga—Zn oxide has a homologous structure and is represented by a composition formula InGaO3(ZnO)m (m is a natural number) (see Non-Patent Document 2).
Furthermore, in 1995, a transistor including an oxide semiconductor was invented, and its electrical characteristics were disclosed (see Patent Document 2).
In 2014, a transistor including a crystalline oxide semiconductor was reported (see Non-Patent Document 3). The transistor in this report includes a c-axis aligned crystalline oxide semiconductor (CAAC-OS) and thus is capable of mass-production and has high electrical characteristics and reliability.
The transistor including an oxide semiconductor has features different from those of the transistors including amorphous silicon or polycrystalline silicon. For example, a display device to which a transistor including an oxide semiconductor is applied is known to have small power consumption. An oxide semiconductor can be formed by a sputtering method or the like, and thus can be used in a transistor included in a large display device. Because a transistor including an oxide semiconductor has high field-effect mobility, a high-performance display device in which a driver circuit and a pixel circuit are formed over the same substrate can be obtained. In addition, there is an advantage that capital investment can be reduced because part of production equipment for a transistor including amorphous silicon can be retrofitted and utilized.